Climate change (mainly) and progressive "desertification" through poor farming practices and over grazing
An oasis or the Nile River Valley.
The Sahara Desert covers 100 percent of the land it occupies.
Mali is mostly comprised of desert (the Sahara Desert). However, there are fertile areas by the Niger River which runs through the southern portion of Mali.
What do you mean by main land? The Sahara desert is located on the continental mainland of Africa
The Sahel is a region of semi-arid grassland between the Sahara and the Savanna.
The Sahara is a vast desert region in North Africa known for its arid climate and sandy landscapes, while the Sahel is a semi-arid transitional zone south of the Sahara that experiences periodic droughts and supports more vegetation. The Sahel acts as a buffer between the Sahara Desert and the more fertile savannas further south.
The Sahara Desert is expanding. This means it is encroaching upon otherwise good, fertile land. Poor agricultural practices along its southern borders have resulted in increased desertification, so grassland to the south of the Sahara is disappearing at the rate of 50 km every year.
the Sahara desert
Any fertile land in a desert is called an oasis. It is fertile because it has enough water supply originating from a spring or a well.
Back then, the Nile River contained a great number of fertile land. And that fertile land help the Egyptians plant food and crops. In the modern world today, that fertile land no longer exists; it is all just empty lonely desert.
The Sahara desert.
Stranded in the middle of the Sahara desert he knew that his only hope of survival was to find an oasis, for the water and shade which it would provide.